A method called a fusion process is conventionally known as a manufacturing method of a high-quality glass sheet. The fusion process is a method in which molten glass is run down along both side surfaces of a molded body with a cross section of a wedge shape converging downward and also the molten glass is joined and integrated just under a lower edge part of the molded body and while cooling an integrated sheet-shaped glass ribbon, the glass ribbon is drawn downward, thereby molding in a target thickness.
In the fusion process, it is necessary to maintain an atmosphere in the vicinity of the molded body at relatively high temperature so that the molten glass running down along both side surfaces of the molded body runs in a uniform thickness. Also, it is necessary to maintain an atmosphere of the lower portion of the molded body at relatively low temperature so that the glass ribbon separate from the lower edge part of the molded body does not contract in a width direction by surface tension.
Hence, a technique for providing partition walls just under a molded body and respectively arranging the two partition walls from both sides of a glass ribbon so as to approach the glass ribbon as close as possible in order to inhibit an atmosphere in the vicinity of the molded body from mutually influencing an atmosphere of the lower portion of the molded body is conventionally known (for example, see Patent Documents 1 and 2).